BMI Calculator
Calculate adult BMI in metric or imperial units, view a reference weight range, and compare standard or lower Asian BMI thresholds.
Adult BMI uses the same height-and-weight formula for males and females. Age helps us identify when adult guidance applies.
Quick unit converters
Convert either way, then use the values in your BMI calculation.
Feet & inches ↔ centimetres
1 foot = 30.48 cm · 1 inch = 2.54 cm
Kilograms ↔ pounds
1 lb = 0.45359237 kg
BMI is a screening measure, not a diagnosis. It does not directly measure body fat and may be misleading with high muscle mass or in older adults. Children need age- and sex-specific growth charts. During pregnancy, ask your maternity team about weight assessment.
About this tool
For adults aged 18 or over who are not pregnant. BMI equals kilograms divided by metres squared. Standard thresholds are 18.5, 25 and 30; optional Asian thresholds follow NICE at 18.5, 23 and 27.5. Age and sex do not change the adult BMI formula.